1. Field of the Invention
The present invention relates in general to automotive engine cooling systems, and, more specifically, to a multi-port valve for distributing and controlling coolant flow to cooling system circuits.
2. Description of the Related Art
Conventional cooling systems for internal combustion engines include a coolant circuit within an engine block, a radiator, a fan, a heater core, water pump, and various hoses and clamps. They also include a thermostat and/or various valves to control the flow of coolant in response to the temperature of the coolant, demand for heating of the passenger compartment, and other factors.
When an engine is first warming up after being started, it is known to have the coolant flow bypass the radiator so that the coolant and the engine warm up more quickly. Quicker warming leads to reduced engine emissions, improved fuel economy, and improved engine performance since reaching an optimal engine operating temperature in faster time means less time spent in cold start emissions mitigation strategies. Vehicles using diesel systems may use an oil-cooler circuit in place of the bypass circuit.
The switching of coolant flow between a bypass circuit and the radiator circuit is conventionally performed by a thermostat. A typical thermostat uses a wax motor to drive a valve between one position in which all coolant is directed through the bypass and none to the radiator and another position in which all coolant is directed through radiator and not through the bypass. Some thermostats may gradually cut off bypass flow while radiator flow gradually increases.
Internal combustion engine technology is producing engines of higher efficiency and increasingly sophisticated control methods. This has increased the need for fast warm up times and precise control of engine operating temperatures, which have not been adequately attained with conventional cooling systems. Furthermore, delays in warming up of the engine also delay the availability of heat in the passenger compartment.
A passive 2-way valve separate from the thermostat has been used to direct coolant to a heater core when warm air is being demanded in the passenger compartment. Other valves may also be included for either cooling or heating other vehicle components, such as cooling of electronic modules or heating of seats. Achieving these additional functions becomes expensive not only because of the proliferation of valves, but also because of the proliferation of separate actuators and wiring, cables, or hydraulic or pneumatic (e.g. vacuum) lines required to control them.
Multi-port rotary valves have generally been known for regulating more than 2 valve ports. U.S. Pat. No. 5,529,026 discloses a single-point coolant diversion to various ports of an engine cooling system. However, this and other multi-port valves that utilize an actuator to drive a rotary valve have required an external mounted actuator with an external gearing or coupling to drive the rotary valve. This requires additional packaging space exterior to the valve body. Also, should an actuator be used to drive the valve, if an actuator failure or loss of control signal occurs, the valve must be returned to a default position so that the proper coolant flow can be maintained to cool the system. This often requires the use of a clutch located interior or exterior to the actuator to release the gearing from a drive unit. The addition of the clutch either interior or exterior to the actuator adds more components, which adds to the expense, and requires additional packaging space.
Furthermore, a majority of the multi-port rotary valves incorporate a coolant flow inlet port offset (not coaxial) from a radiator port. Those multi-port rotary valves that do have the inlet port and the radiator port co-axial incorporate the default position at a distal end of the rotary valve rotation.